A Treatise On The Principles And Practice Of Dock Engineering

20 DOCK ENGINEERING. régulations of the Board of Agriculture require the animais to be inspected before any part of the cargo is discharged, and to be slaughtered at the point of disembarkation. Cost of Dock Construction.—A point of very marked, and even vital, interest to the engineer is the approximate cost of a projected undertaking, and any guidance in forming his estimates, or in affording a basis for com- parison with works of a similar nature elsewhere, is readily welcomed ; but information sufficiently reliable for the purpose is rarely available in dock engineering, on account of the extreme diversity of circumstances under which its operations are carried out. The cost of dock construction vaiies exceedingly, depending, as it does, upon such mutable conditions as the difficulties appertaining to each particular site, the current price and trans- port rate of material, the cost of labour, combined with an extremely wide range of equipment. Some docks have gates; others do not need them. Some are bordered by open quays ; others are provided with sheds, several storeys in height. There is, in fact, absolutely no uniformity of treatment, and anything in the nature of comparison is practically impossible. The following statistics are inserted by way of interest merely. They are of na value whatever as a standard of cost in localities, and under circumstances other than those which they actually represent:— Actual Cost of Docks and their Equipment per Acre of Water Victoria Dock, Dundee, . . £10,600 Barry Docks, South Wales, . 12,950 West India Docks, London, . 15,000 Prince of Wales Dock, Swansea, 18,600 Victoria Harbour, Greenock, . 21, ,30 Surface. :Alexandra Dock, Liverpool, . £23,300 Albert Dock, Hull, . . . 24,300 Queen’s Dock, Glasgow, . . 24,450 Alexandra Dock, Hull, . - 28,900 Canada Branch Dock, Liverpool, 40,000 Fresh Water Supply.—An important point in dock design, which must not be overlooked, is the provision of a supply of clean water to replenish the waste due to leakage and other causes, and also to prevent the dock from becoming foul and insanitary. The writer’s experience of leakage through gates and of losses through lockage under normal circumstances at the port of Liverpool, is that the combined depression does not exceed an inch per hour over the whole water surface, but in other localities it may be more or less according to the conditions which obtain. On the sea coast and in estuaries, the tide may be relied upon to effect the necessary augmentation and changes in an efficient manner, but in rivers highly charged with sedi- ment, such extraneous means of supply cannot be adopted without incurring considerable expense in the removal of sand and silt from the interior of the dock. In this case it is preferable to seek fresh water from some inland source to feed the dock, the water in which must always be maintained at a higher level than that of the river. Where this plan is inapplicable the difficulty may be overcome by constructing between the river and the dock a